A printer apparatus which carries out a given printing operation on paper and issues the paper is provided with various sensors for detecting various errors. Most of the sensors for detecting various errors are used to detect only one kind of errors, for example, a cover-open sensor merely confirms whether or not the cover of the printer apparatus is closed correctly, and a jam sensor merely confirms whether or not paper jam occurs. Thus, it is considered to use one sensor to realize various detections including the detection on the error opening of a cover and the detection on the double-feeding of paper.
In paper jam detection, if a printer using cut paper and the like finishes the conveyance of the length of a paper, the receiving signal of a detection sensor is changed. Thus, the detection on paper jam can be carried out by confirming the signal. However, it is difficult to detect the jam of paper wound into a roll shape since the paper is continuous until it is cut. It is known that the detection on the paper jam can be realized by using the paper on the back side of which a black mark for detecting the conveyance of paper is arranged, however, in this detection, it is needed to use dedicated paper and sensors, and it is incapable of detecting other errors while detecting paper jam.